Methods of reducing polystyrene foams using dibasic esters with extruders

ABSTRACT

The present invention is directed to novel polystyrene foam reduction recycling compositions and methods that solve the volume problem of recycling polystyrene foam materials while simultaneously allowing the easy and inexpensive shipment of the foamed materials after reduction in volume by use of one or more dibasic ester compositions in combination with one or more low heat based mechanical extruders. The methods of the present invention are applicable to all types of expanded or foamed polystyrene materials known to those of skill in the art.

FIELD OF THE INVENTION

This invention provides novel methods employing chemical agents withextruders to reduce polystyrene foam plastics to a compact form using adibasic ester-based chemical agent in liquid form which reduces thepolystyrene foam to a sludge-like material that is safe to ship andgreatly reduces its volume of waste.

BACKGROUND OF THE INVENTION

Polystyrene foam has been used for some time as packing material,insulation material, structural materials and other various uses.Polystyrene foams exhibit many useful qualities in a wide variety offields. The foams usefulness is based partly on its cost effectiveness,its inherent insulating qualities and the ease with which it may beformed into a great variety of shapes. For instance, the food handlingindustry has found polystyrene foam packaging to be of great use in thepackaging of food products for its consumers. In addition, the buildingindustry has found a large variety of uses for the foam. The chiefconcern for the various uses of the foam has been the amount of wastethat is generated by the use of polystyrene foam products.

Generally speaking, polystyrene foam has primarily caused great concernbecause of its lack of biodegradability. The foam by its very naturetakes up a great deal of volume per weight, which has caused manyindividuals to question its overall commercial usefulness when comparedto the overall possible detrimental environmental impact. Theenvironmental impact includes the accelerated rate that landfill spaceis being used up at because the foam, in its useful form, takes a largeamount of space per weight of waste. Moreover, the transportation of thefoam waste is very inefficient due to the volume weight ratio.Typically, the waste material is transported from a restaurant facilityto a waste area. This transportation usually involves motor vehicletransport. The vehicles can transport a much greater weight of refusethan can be placed in the vehicle due to the large volume thepolystyrene foam takes up. Therefore, the transportation of polystyrenefoam products in general is very inefficient because the full capacityof the shipping means is not utilized.

Also, in the industry it has been very difficult to find an effectivemethod of recycling the polystyrene foam products. This is due in partto the shipping cost described above and the cost of the process of theactual recycling. There is a therefore a continued need for apolystyrene foam volume reduction method to allow use of moreconventional plastic recycling and processing equipment. At the present,very expensive and specialized processing equipment and extrapolystyrene foam compaction steps are required to recycle polystyrenefoam products.

One approach to the recycling of polystyrene foam is to use chemicals toreduce the foam. The basic problem in the industry, however, is that thechemicals that are often considered the most obvious to use are verytoxic to the environment with the result that they are often banned byenvironmental legislation or regulations. One chemical series, pineneand terpenes such as d-limonene can reduce the foam volume. Thisapproach is interesting but unfortunately it fails to be an effectivemethod in some cases. Specifically, the cost of d-limonene is directlyrelated to the crop levels of citrus products. Accordingly, when thereis a problem with the production of citrus-based products due to badgrowing conditions, it directly effects the price to recycle foamproducts to the point where it may no longer be cost effective.

Moreover, prior approaches evidence an inconsistent activity incollapsing polystyrene foams that has not previously been addressed inthe industry. For example, while heat activation of the terpenes hasremoved this problem (U.S. Pat. No. 5,223,543, the entire contents ofwhich are incorporated herein by reference), it adds to the overall costof recycling and it involves a volatile environmentally compromisingchemical. The chemicals used in the '543 patent were problematic forshipping due to their flash point. They are highly volatile andtherefore extra precautions have to be taken when shipping such productsthat ultimately make use of such chemicals cost-ineffective. Moreover,the process used in the '543 patent was basically vapor phase, providingfor possible emissions of vapors which were a Clean Air Act Problem.Thus there continues to be a major need for a polystyrene foam reductionprocess that uses low volatility agents.

Also, the use of volatile chemicals presents another problem for therecycling efforts of polystyrene foam products. The chemicals usedheretofore suffer great loss in the recycling process due toevaporation. This makes the recycling materials vary hard to recover tobe used again in the recycling process. As such, it greatly increasesthe cost to the recycling efforts. The evaporated chemicals would alsopotentially increase the danger of an accident during the recyclingprocess due to unacceptable flash points of the chemicals. This isespecially true were the best performance of the chemicals is aided bythe application of heat to the recycling process. Ultimately, thevolatile chemicals and heat required lead to conditions during therecycling process that are potentially very dangerous.

An ideal process would have little need for the heat activation step ofU.S. Pat. No. 5,223,543 and would further allow viscous and higherboiling point materials to be employed. Ideally, these materials wouldnot require longer residence times prior to recycling. A long time woulddelay the sequence of breaking down the polystyrene foam products andshipping of same. This increase in residence times adds to the overallcost of the recycling process. Also, the need to decrease residence timemust be balanced with reduced heat activation in combination with higherboiling point materials whose combination would result in a heretoforeunobtainable efficient and safe chemical reactant. In addition, it wouldbe most desirable to have the product or sludge of the polystyrene foamcollapsing reactions safely shippable. It would also be advantageous toidentify effective compounds that insulate the polystyrene foam reducermarket from the wide price variation of the orange crop relatedd-limonene market.

Also, it would be desirable to have a compound that is environmentallyfriendly. Part of the major problem with the past use of foam productsis that they now occupy a great deal of space in our landfills.Therefore, there is a significant need for an agent that can be used atthese landfills on foam, which has already been deposited intolandfills. The only way to accomplish this is by the application of afoam reducing agent that has no detrimental side effects on theenvironment.

In a prior effort to address some of these needs, Katz et al. wererecently issued U.S. Pat. No. 6,743,828 which is directed to apolystyrene foam reduction agent consisting of dibasic esters and aprocess using a liquid contact with polystyrene foam wherein the higherboiling temperature of the dibasic esters and contact with the liquidprovides a volume reduction process and less evaporation loss as well assafer transportation of the chemicals and the polystyrene in its reducedstate. The foam reduction agent consisting of dibasic esters and theprocess employed results in a reduced sludge that is also recyclable tosuperior quality raw polystyrene foam beads and the reduction agents arerecoverable for future use.

In addition to the use of the dibasic esters to reduce the volume ofpolystyrene foam or expanded polystyrene foam (EPS), traditional methodsused in the normal course of reducing and/or recycling polystyrene foamor expanded polystyrene foam (EPS) typically involve the use ofsignificant ancillary equipment including, but not limited to, thin filmevaporators (TFEs), and/or machines commonly referred to in the art as“fluffers”. Even if the temperature is considered low in the art, theTFE and/or fluffer time factors come into play and in the normal courseof processing this results in a burning of the polystyrene foam orexpanded polystyrene foam. It would therefore be beneficial in theprocessing stage for the polystyrene foam or expanded polystyrene foamto have a short residence time so as to shorten the thermal history ofthe polystyrene. The beaded polystyrene end product of such a processwould be of higher quality and would be less likely to degrade.

Notwithstanding the usefulness of the prior polystyrene foam reductionrecycling systems using dibasic or dialkyl esters, there is a continuingneed in the art to develop other more versatile polystyrene foamreduction recycling systems to enhance the efficiency and full range ofrecycling possibilities. This invention solves these and other long feltneeds by providing compositions and methods utilizing dibasic esters,low vapor pressure dibasic esters or functional derivatives thereof incombination with one or more extruders in a polystyrene foam reductionrecycling system.

SUMMARY OF THE INVENTION

In general, the present invention is directed to novel polystyrene foamreduction recycling compositions and methods that solve the volumeproblem of recycling polystyrene foam materials while simultaneouslyallowing the easy and inexpensive shipment of the foamed materials afterreduction in volume by use of one or more dibasic ester compositions incombination with one or more low heat based mechanical extruders. Themethods of the present invention are applicable to all types of expandedor foamed polystyrene materials known to those of skill in the art.

In one aspect, a method of reducing/recycling polystyrene foam isprovided comprising the steps of (a) providing polystyrene foam; (b)applying to said polystyrene foam a solution comprising: one or morestandard dibasic ester (DBE) compositions selected from the groupconsisting of dimethyl glutarate, dimethyl adipate, and dimethylsuccinate; (c) subjecting the resultant polygel to a low source of heatover a temperature range not to exceed 200-300° C.; (d) subjecting theresultant polygel to one or more extruders over a temperature range notto exceed 200-300° C.; and (e) recapturing the dibasic esters; whereinsaid recaptured dibasic esters are reused or recycled and the resultantpolystyrene foam polygel may be recycled into high quality beadedpolystyrene foam.

In yet another aspect, a method of reducing/recycling polystyrene foamis provided comprising the steps of (a) providing polystyrene foam; (b)applying to said polystyrene foam a solution comprising: one or more lowvapor pressure dibasic ester (LVP-DBE) compositions selected from thegroup consisting of dimethyl glutarate, dimethyl adipate, and dimethylsuccinate; (c) subjecting the resultant polygel to a low source of heatover a temperature range not to exceed 200-300° C.; (d) subjecting theresultant polygel to one or more extruders over a temperature range notto exceed 200-300° C.; and (e) recapturing the low vapor pressuredibasic esters; and wherein said recaptured low vapor pressure dibasicesters are reused or recycled and the resultant polystyrene foam polygelmay be recycled into high quality beaded polystyrene foam.

In another aspect, a method of reducing/recycling polystyrene foam isprovided comprising the steps of (a) providing polystyrene foam; (b)applying to said polystyrene foam a solution comprising: (i) one or moreterpenes or isopernoids or any combination thereof and (ii) one or moresurfactants; (c) subjecting the resultant polygel to a low source ofheat over a temperature range not to exceed 200-300° C.; (d) subjectingthe resultant polygel to one or more extruders over a temperature rangenot to exceed 200-300° C.; and (e) recapturing the terpenes orisopernoids; and wherein said recaptured terpenes or isopernoids arereused or recycled and the resultant polystyrene foam polygel may berecycled into high quality beaded polystyrene foam.

In each of the aforementioned aspects and embodiments, the method ofreducing a volume of polystyrene foam may further comprise one or morevegetable oils.

In yet another aspect, the invention relates, in part, to a novelpolystyrene low heat treatment extruder recycling system comprising thesteps of (a) exposing polystyrene foam in a container to a solution ofspecific esters comprising dimethyl glutrate [CAS # 1119-40-0] anddimethyl adipate [CAS# 627-93-0], wherein the esters specificallyexclude dimethyl succinate in weight percentage amounts greater than 1%;(b) optionally covering said container; (c) subjecting the resultantpolygel to a low source of heat over a temperature range not to exceed200-300° C.; (d) subjecting the resultant polygel to one or moreextruders over a temperature range not to exceed 200-300° C.; (e)optionally supplementing polystyrene foam until maximum reduction isachieved and (f) recapturing the dibasic esters; and wherein saidrecaptured dibasic esters are reused or recycled and the resultantpolystyrene foam polygel may be recycled into high quality beadedpolystyrene foam.

In another aspect, a method of reducing/recycling polystyrene foam isprovided comprising the steps of (a) providing polystyrene foam; (b)applying to said polystyrene foam a solution comprising: (i) one or morelow vapor pressure dibasic ester compositions selected from the groupconsisting of dimethyl glutarate, dimethyl adipate, and dimethylsuccinate; (ii) one or more dibasic ester compositions selected from thegroup consisting of dimethyl glutarate, dimethyl adipate, and dimethylsuccinate or (iii) (a) one or more terpenes or isopernoids or anycombination thereof and (b) one or more surfactants; or any combinationthereof of (i)-(iii); (c) subjecting the polygel to a low source of heatover a temperature range not to exceed 200-300° C.; (d) subjecting thepolygel to one or more extruders over a temperature range not to exceed200-300° C.; and (e) recapturing the dibasic esters, the low vaporpressure dibasic esters and/or the terpenes or isopernoids; and whereinsaid recaptured dibasic esters, low vapor pressure dibasic esters and/orthe terpenes or isopernoids are reused or recycled and the resultantpolystyrene foam polygel may be recycled into high quality beadedpolystyrene foam.

In yet another aspect, the present invention provides a novelpolystyrene low heat treatment extruder recycling system comprising aLVP-DBE composition that exhibits one or more of the followingcharacteristics: (a) a significantly lower vapor pressure than standardDBE, (b) the distillation range of the solvent is narrower, (c)chemically more stable than standard DBE, (d) that is incompatible orcan react with, inter alia, strong oxidizers, acids, alkalies, etc., (e)that will not undergo polymerization, (f) that reduces foamedpolystyrene at a rate of action that equals or exceeds that of standardDBE, (g) that exhibits a greater holding capacity than standard DBE, (h)that exhibits a higher flash point than standard DBE, (i) that is notregulated as a hazardous material by DOT, IMO, or IATA, and (j) forwhich none of the components present in the LVP-DBE composition arelisted by IARC, NTP, OSHA or ACGIH as a carcinogen.

In yet another aspect, the invention relates, in part, to a novelpolystyrene low heat treatment extruder recycling system comprisingexposing said foams to liquid sprays of specific esters exhibiting oneor more of the aforementioned characteristics.

In yet another aspect, the invention relates, in part, to a novelpolystyrene low heat treatment extruder recycling system comprisingexposing said foams to liquid sprays of specific esters comprisingdimethyl glutarate [CAS # 1119-40-0] and dimethyl adipate [CAS#627-93-0], wherein the ester specifically excludes dimethyl succinate inweight percentage amounts greater than 1%, and wherein said estersexhibit one or more of the aforementioned characteristics.

In yet another aspect, the invention relates, in part, to a novelpolystyrene low heat treatment extruder recycling system comprisingexposing said foams to liquid sprays of specific esters, wherein theester is selected from the group consisting of dimethyl glutarate [CAS #1119-40-0] and dimethyl adipate [CAS# 627-93-0], wherein the estersspecifically exclude dimethyl succinate in weight percentage amountsgreater than 1%, and wherein said esters exhibit one or more of theaforementioned characteristics.

In yet another aspect, the present invention provides a novelpolystyrene low heat treatment extruder recycling system in which therecaptured standard dibasic ester, LVP-DBE and/or terpene or isopernoidcomposition is useful for rendering organic polymeric coatings andfinishes such as paints, varnishes, lacquers, shellacs, gums, naturaland synthetic resins removable from a wide range of coatings andsurfaces such as, for example, and not by way of limitation, wood,metal, and plastic. An important feature of the recaptured standarddibasic ester, LVP-DBE and/or terpene or isopernoid composition is thatit provides excellent results without the need of evaporation retardantsor film-forming compounds. Thus, there is no need to include in theformulation such evaporation retardants as paraffin wax or the like,which have the disadvantage that they need to be removed in subsequentprocessing steps. Another feature of the recaptured standard dibasicester, LVP-DBE and/or terpene or isopernoid composition produced by thenovel polystyrene low heat treatment extruder recycling system of thepresent invention is that it has a shelf life in excess of about oneyear to about 10 years.

In one embodiment, the polystyrene foam may be shredded or grinded priorto exposure to the aforementioned specific ester combination using oneor more extruders of the present invention in combination with any othermechanical apparatus known to those of skill in the art for shredding orgrinding polystyrene foam. By converting the polystyrene foam intosmaller fragments, a greater surface area for exposure to the specificester combination is provided thereby affording faster polystyrene foamreduction. Also contemplated for use with the extruders used in themethods of the present invention are certain hot air machines and/ordryers known to those of skill in the art for partially or fully dryingthe polystyrene foam prior to use with the extruder.

In one embodiment, in each of the aforementioned aspects, step (b) ofadding the solution comprising the dibasic esters, the low vaporpressure dibasic esters, and/or the terpenes or isopernoids or anycombination thereof may be carried out without prior treatment of thepolystyrene foam with one or more thin film evaporators or one or morefluffers, and/or one or more dryers.

In each of the aforementioned aspects and embodiments of the low heatextruder polystyrene recycling methods disclosed herein the ratio ofDBE, low vapor pressure DBE and/or the terpene and/or isoprenoid isapproximately one third (wt %) to approximately two thirds (wt %)polystyrene foam or EPS. Any ratio higher than approximately 50% ofsolvent to polystyrene foam or EPS in the low heat extruder polystyrenerecycling methods disclosed herein is not as effective as the extruderis unable to strip or remove the solvent fast enough.

In yet another embodiment, in each of the aforementioned aspects, afterthe step of recapturing the dibasic esters, the low vapor pressuredibasic esters and/or the terpenes or isopernoids, the resultantpolystyrene polygel may optionally be subjected to one or more thin filmevaporators (TFEs) for a time period of approximately 1-2 minutes, butnot to exceed approximately 10 minutes.

In each of the aforementioned aspects and embodiments, the resultanthigh quality beaded polystyrene product so produced has a series ofdesired properties including, but not limited to, a heat index of lessthan about 9, a final concentration of less than about 1-1000 ppm of thestandard DBE composition, LVP-DBE composition, or terpene and/orisoprenoid in the high quality beaded polystyrene product, no evidenceof spleaning, crazing and/or burnt discoloration, and a relatively lowmelt viscosity and molecular weight, or any combination thereof.

Other preferred embodiments of the invention will be apparent to one ofordinary skill in the art in light of what is known in the art, in lightof the following drawings and description of the invention, and in lightof the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a process schematic for a 30 mm devolatilizationextruder.

FIG. 2 depicts a 30 mm devolatilizer screw and barrel arrangement961841_(—)1.

FIG. 3 depicts a rear vent yield versus feed superheat, calculated forsample conditions from adiabatic flash model of polystyrene and dimethylsuccinate.

FIG. 4 depicts a specific energy consumption versus specific rate.

FIG. 5 depicts a melt temperature versus specific rate for samples 5 to14.

DETAILED DESCRIPTION OF THE INVENTION

This invention reveals a method to provide rapid destruction of thecells of polystyrene foams by use of a combination of specific chemicalsof the class of aliphatic dibasic esters, either alone or with otherfoam reduction agents and surfactants that are active and which readilyattack, with no or little heat activation, polystyrene foam and allowseasy recycling. The easy recycling is due to reduced bulk and ease ofstorage of the collapsed polystyrene foam in sludge foam, ease ofprocessing, and economical transportation prior to recycling. Thecollapsed polystyrene foam may be easily and safely transported.

The inventors have unexpectedly found that by using one or moreextruders, operating in the presence of low heat, the DBE and/or LVPDBE, taken either alone or in combination with one or more terpenesand/or isopernoids, may be efficiently recovered or recycled so that thefinal concentration of the DBE, the LVP DBE, the terpenes and/orisopernoids in the reduced polystyrene foam and/or EPS is less thanapproximately 1 ppm. Such low final concentrations of DBE and/or LVP DBEhave heretofore not been previously obtainable in the polystyrene foamrecycling industry.

The inventors have also unexpectedly found that by use of one or moreextruders in the presence of low heat the DBE and/or LVP DBE, eitheralone or in combination with one or more terpenes and/or isoprenoids,the recovered or recycled reagents react faster when used to reduce thepolystyrene as the amount of water is vented away from the DBE and/orLVP DBE. Thus, the less water in the faster the reaction time withexpanded polystyrene foam or the polystyrene foam. The venting processis accomplished by use of one or more extruders in the presence of lowheat.

Standard Dibasic Ester Compositions

Specifically included within the scope of the polystyrene foam reductionlow heat treatment extruder recycling system of the present invention isthe use of standard dibasic esters including, for example, and not byway of limitation, as disclosed in the inventors' U.S. Pat. No.6,743,828.

Also specifically included within the scope of the polystyrene foamreduction low heat treatment extruder recycling system of the presentinvention is the use of DBE, DBE-4, and DBE-9 as specifically set forthin Table 1, infra.

Low Vapor Pressure Dibasic Ester (LVP-DBE) Compositions

In those embodiments of low heat treatment extruder methods of reducingpolystyrene foam that use low vapor pressure dibasic esters, the lowvapor pressure dibasic esters of the present invention comprise acomposition of LVP-DBE comprising dimethyl glutarate [CAS # 1119-40-0]and dimethyl adipate [CAS# 627-93-0]. In one embodiment, the novelpolystyrene foam reduction recycling system of the present inventionfurther comprises a composition of LVP-DBE comprising dimethyl glutarate[CAS # 1119-40-0], dimethyl adipate [CAS# 627-93-0] and dimethylsuccinate (CAS# 106-65-0), wherein the weight percentage of dimethylsuccinate is 1% and less. For example, and not by way of limitation,1.0%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, and anynumerical values there between are specifically permitted for use in thepolystyrene foam reduction recycling system of the present invention.Other LVP-DBE-based compositions that may be used in the novelpolystyrene foam reduction low heat treatment extruder recycling systemof the present invention include LVP-DBE-2, LVP-DBE-3, LVP-DBE-5,LVP-DBE-6, and LVP-DBE-1B as specifically set forth in Table 1, infra.

In those embodiments of the low heat treatment extruder methods ofreducing polystyrene foam that use low vapor pressure dibasic esters,specifically excluded within the scope of those embodiments is the useof non-low vapor pressure DBE. Also specifically excluded within thescope of the polystyrene foam reduction low heat treatment extruderrecycling system of the present invention is the use of DBE, DBE-4, andDBE-9 as specifically set forth in Table 1, infra. Also specificallyexcluded within the scope of the polystyrene foam reduction low heattreatment extruder recycling system of the present invention is the useof dimethyl succinate (CAS# 106-65-0) in weight percentage amountsgreater than 1%.

In one embodiment of the polystyrene foam reduction low heat treatmentextruder recycling system of the present invention, the percentage ofdimethyl glutarate in the LVP-DBE composition of the present inventionis in the range of between about 5% and about 98% weight percent. In oneembodiment, the percentage of dimethyl adipate in the LVP-DBEcomposition of the present invention is in the range of between about20% and about 98.5% weight percent. In one embodiment, the percentageweight of total diesters in the LVP-DBE composition of the presentinvention is at least 98.5% weight percent, with an average weightpercentage of approximately 99.4-99.7%. It is intended herein that theranges recited also include all those specific percentage amountsbetween the recited range. For example, the range of about 20 to 98.5%also encompasses 21 to 97.5% weight percent, 22 to 98.5% weight percent,21 to 96.5% weight percent, etc., without actually reciting eachspecific range therewith. In another embodiment of the polystyrene foamreduction low heat treatment extruder recycling system of the presentinvention, the percentage of dimethyl glutarate in the LVP-DBEcomposition of the present invention is in the range of between about 2%and about 40% weight percent and the percentage of dimethyl adipate inthe LVP-DBE composition of the present invention is in the range ofbetween about 10% and about 50% weight percent.

In yet another aspect, the present invention provides a polystyrene foamreduction low heat treatment extruder recycling system comprising acomposition of LVP-DBE that exhibits a significantly lower vaporpressure than standard DBE. In one embodiment, the lower vapor pressureexhibited by the LVP-DBE composition of the present invention is in therange of between about 0.01 to about 0.001 mm Hg @ 20° C. (68° F.),compared to the vapor pressure of standard DBE which is in the range ofbetween about 0.10 to about 0.02 mm Hg @ 20° C. (68° F.). Such lowervapor pressure is important because it translates into a healthier workenvironment and a lower inhalation risk for potential users andrecyclers. The lower vapor pressure also minimizes any apparent odor inthe work area for users and recyclers.

In yet another aspect, the present invention provides a polystyrene foamreduction low heat treatment extruder recycling system comprises acomposition of LVP-DBE that exhibits a significantly lower vaporpressure than standard DBE, which LVP-DBE meets the low vapor pressurecriteria established by the California Air Resources Board for volatileorganic compounds in consumer products per California Code ofRegulations, Title 17, Division 3, Chapter 1, Subchapter 8.5, Article 2,Section 94508(a) 80(A), the entire contents of which are incorporatedherein by reference.

In yet another aspect, the present invention provides a novelpolystyrene foam low heat treatment extruder recycling system comprisinga composition of LVP-DBE that exhibits a significantly lower vaporpressure than standard DBE, which LVP-DBE meets the exemption criteriafor consumer products per EPA 40 C.F.R. Section 59.203(f)1, the entirecontents of which are incorporated herein by reference.

In one embodiment, the novel polystyrene foam heat treatment extruderrecycling system of the present invention further comprises a twocomponent composition of LVP-DBE (for example, dimethyl adipate anddimethyl glutarate) that provides simplified distillation or otherrecycling methods.

In yet another embodiment, the novel polystyrene low heat treatmentextruder recycling system of the present invention comprises a threecomponent composition of LVP-DBE in which the distillation range of thesolvent used to reduce the polystyrene or EPS is unexpectedly narrowerthan that found in U.S. Pat. No. 6,743,828. Such narrower distillationranges result in lower equipment costs, better control and lowerproduction and use costs. In one embodiment, the distillation range ofthe solvent of the LVP-DBE composition of the present invention is inthe range of between about 210 to about 225° C. (about 410 to about 437°F.), compared to the distillation range of the solvent of standard DBEwhich is in the range of between about 196 to about 225° C. (about 385to about 437° F.). The unexpectedly narrower distillation range of thesolvent of the LVP-DBE composition serves to narrow down the boilingrange by over 9%. Thus, the range can now be narrowed to reflect thecloser boiling point which will result in a better polystyrene bead. Byuse of a higher heat ratio in the LVP-DBE polygel, breakdown of theLVP-DBE will not occur as easily.

In yet another aspect, the present invention provides a novelpolystyrene foam low heat treatment extruder recycling system comprisinga LVP-DBE composition that is chemically more stable than standard DBE.Since the vapor pressure of the LVP-DBE is lower, the polystyreneproduct is more stable and has certain properties that make LVP-DBE abetter choice to use in a given work place. For example, in oneembodiment, the LVP-DBE composition will not remove paint or adhesivesas quickly as standard DBE.

In yet another aspect, the present invention provides a novelpolystyrene foam low heat treatment extruder recycling system comprisinga LVP-DBE composition that is incompatible or can react with, interalia, strong oxidizers, acids, alkalies, etc.

In yet another aspect, the present invention provides a novelpolystyrene foam low heat treatment extruder recycling system comprisinga LVP-DBE composition that will not undergo polymerization.

In yet another aspect, the present invention provides a novelpolystyrene foam low heat treatment extruder recycling system comprisinga LVP-DBE composition that reduces foamed polystyrene at a rate ofaction that equals or exceeds that of standard DBE. Thus, in oneembodiment, in outdoor conditions when the temperature is warm, thelower vapor pressure DBE will not evaporate as quickly and thereforewill be more effective in reducing expanded polystyrene foam (EPS).

In yet another aspect, the present invention provides a novelpolystyrene foam low heat treatment extruder recycling system comprisinga LVP-DBE composition that exhibits a greater holding capacity thanstandard DBE. In one embodiment, such greater holding capacity atambient temperature approaches approximately 55%-approximately 75% ofpolystyrene with the remainder being solvent (LVP-DBE), whereas theholding capacity for a polystyrene low heat treatment extruder recyclingsystem using standard DBE approaches approximately 0-50%. Such greaterholding capacity is demonstrated by virtue of the lower viscosity of thesolution at equal concentrations. This lower viscosity leads to a morecost effective use of the solvent as a more concentrated polygel can beproduced which makes recycling of polystyrene foam more effective.

In yet another aspect, the present invention provides a novelpolystyrene foam low heat treatment extruder recycling system comprisinga LVP-DBE composition that exhibits a higher flash point than standardDBE. In one embodiment, the flash point of the LVP-DBE composition ofthe present invention is in the range of between about 102 to about 104°C. (about 216 to about 219° F.), compared to the flash point of standardDBE which is about 100° C. (about 212° F.). Such higher flash pointsleads to increased safety for the user and recycling process and willminimize transportation restrictions.

In yet another aspect, the present invention provides a novelpolystyrene foam low heat treatment extruder recycling system comprisinga LVP-DBE composition that is not regulated as a hazardous material byDepartment of Transportation (DOT), International Maritime Organization(IMO), or International Air Transport Association (IATA).

In yet another aspect, the present invention provides a novelpolystyrene low heat treatment extruder recycling system comprising aLVP-DBE composition for which none of the components present in theLVP-DBE composition are listed by International Agency for Research onCancer (IARC), National Transportation Program (NTP), OccupationalHealth and Safety Organization (OSHA) or American Conference ofIndustrial Hygienists (ACGIH) as a carcinogen.

In yet another aspect, the present invention provides a novelpolystyrene low heat treatment extruder recycling system comprising aLVP-DBE composition that exhibits biodegradability as measured by the28-day closed bottle test. The LVP-DBE composition was tested forbiodegradability using the 28-day closed bottle test. A minimum of 60%biodegradation must be reached in a 14 day window after exceeding the10% level in order to pass this test and be rated as readilybiodegradable. All of the components of the low heat treatment extruderrecycling system of the present invention pass this test and, therefore,DBE-LVP is considered readily biodegradable. In one embodiment, thebiodegradability of the dimethyl glutrate in the LVP-DBE composition ofthe present invention is in the range of between about 70% at day 7 andabout 84% at day 14%. In one embodiment, the biodegradability of thepercentage of dimethyl adipate in the LVP-DBE composition of the presentinvention is in the range of between about 58% at day 7 and about 84% atday 14. In one embodiment, the biodegradability of the dimethylsuccinate in the LVP-DBE composition of the present invention is in therange of between about 80% at day 7 and about 90% at day 22.

The method of the present invention involves the exposure of said foamsto liquid sprays of specific esters comprising LVP-DBEs that exhibit oneor more of the following characteristics: (a) a significantly lowervapor pressure than standard DBE, (b) the distillation range of thesolvent is narrower, (c) chemically more stable than standard DBE, (d)that is incompatible or can react with, inter alia, strong oxidizers,acids, alkalies, etc., (e) that will not undergo polymerization, (f)that reduces foamed polystyrene at a rate of action that equals orexceeds that of standard DBE, (g) that exhibits a greater holdingcapacity than standard DBE, (h) that exhibits a higher flash point thanstandard DBE, (i) that is not regulated as a hazardous material by DOT,IMO, or IATA, and (j) for which none of the components present in theLVP-DBE composition are listed by IARC, NTP, OSHA or ACGIH as acarcinogen. Examples of DBE dibasic esters are known to those of skillin the art and include for example, and not by way of limitation, thoselisted in Table 1 infra.

In addition to the aforementioned list of properties for the LVP-DBEcomposition for use in the polystyrene low heat treatment extruderrecycling system of the present invention, the specific properties ofeach of the LVP-DBE-2, LVP-DBE-3, LVP-DBE-5, LVP-DBE-6, and LVP-DBE-1BDBE Dibasic Ester compositions as specifically set forth in Table 1infra are also included as if specifically set forth herein, includingfor example, and not by way of limitation, ester content (wt. %, min.),water content (wt. %, max.), acid number, mg KOH/g, max., color, APHA,max., turbidity, max., methanol, wt %, isobutanol, wt %, molecularweight, specific gravity at 20/20° C., density at 20° C. (lb/gal),distillation range, ° C., vapor pressure at 20° C. (mm Hg), solubilityin water, wt % at 20° C., water solubility in DBE, wt % at 20° C.,freezing point, ° C., flashpoint, Tag closed cup, ° C., auto ignitiontemperature, ° C., latent heat of vaporization, cal/g, viscosity at 25°C., cst, and properties of the solvent including, for example, and notby way of limitation, non-polar, polar, hydrogen bonding, surfacetension at 20° C., dynes/cm, and electrical resistance at 24° C., MegOhms, or any combination thereof.

The above-listed characteristics, as well as any other characteristicsprovided in Table 1 infra, confer superior and unexpected results,properties, and advantages to the LVP-DBE composition for its use in thepolystyrene low heat treatment extruder recycling system of the presentinvention compared to the standard DBE composition as used in U.S. Pat.No. 6,743,828. The aforementioned features and benefits of using theLVP-DBE composition of the present invention translate into a strongercommitment for more responsible stewardship of the environment andprovide an excellent example of the concept of closed-loop recycling.TABLE 1 DBE Dibasic Esters Specification DBE DBE-2 DBE-3 DBE-4 DBE-5DBE-6 DBE-9 DBE-IB Ester content, 99.0  99.0  99.0  98.5  99.0  99.0 99.0  98.5  wt. %, min. Water content,  0.10  0.10  0.20  0.04  0.10 0.05  0.10 0.1 wt. %, max. Acid number, mg  0.30  1.00  1.00  0.50 0.50  1.00  0.50  1.00 KOH/g, max. Dimethyl 10-25 20-28 85-95 0.1 max.0.2 max. 98.5 min. 0.3 max. 10-20^(f) adipate, wt % Dimethyl 55-65 72-78 5-15 0.4 max. 98.0 max.   1.0 max. 65-69 55-70^(f) glutarate, wt %Dimethyl 15-25 1.0 max. 1.0 max.  98.0 max.  1.0 max. 0.15 max. 31-3520-30^(f) succinate, wt % Color, APHA, max 15 max. 15 max. 15 max.  15max.  15 max.   15 max.  15 max. 15 max. Turbidity, max.  5 max.  5 max.5 max.   5 max.   5 max.   5 max.   5 max.  5 max. Typical CompositionEster content, 99.5  99.5  99.5  99.5  99.5  99.0  99.0  99.5  wt. %,min. Dimethyl 21   24   89   — 0.1 99   0.2 21^(f)  adipate, wt %Dimethyl 59   75   10   0.3 99   <0.5   66   59^(f)  glutarate, wt %Dimethyl 20   0.3 0.2 98   0.4 <0.1   33   20^(f)  succinate, wt %Methanol, wt %  0.20 <0.1   <0.1   <0.1   <0.1   <0.1   <0.1   N/AIsobutanol, wt % N/A N/A N/A N/A N/A N/A N/A 0.2 Water, wt %  0.05  0.02 0.04  0.02  0.03  0.03  0.04  0.05 Physical Properties (typical values)Molecular Weight 159^(a)   163^(a)   173^(a)   146    160    174   156^(a)   242    Specific gravity at   1.092^(c)   1.081^(c)   1.068^(c) 1.121  1.091  1.064   1.099^(c) 0.958-0.960   20/20° Density at 20° C.  9.09^(c)   9.00^(c)   8.89^(c)  9.33  9.08  8.86   9.18^(c)   7.97^(c)(lb/gal) Distillation 196-225 210-225 215-225 196    210-215 227-230196-215 275-295   Range, ° C. Vapor Pressure at   0.20^(c)   0.04^(c)  0.02^(c)  0.13  0.05  0.01   0.07^(c)  <0.01^(c) 20° C. (mm Hg)Solubility in water, 5.3 4.2 2.5 7.5 4.3 2.1 ca. 5   <0.1   wt % at 20°C. Water Solubility in 3.1 2.9 2.5 3.8 3.2 2.4 ca. 3.5 0.6 DBE, wt % at20° C. Freezing Point, ° C. −20^(c)   −13^(c)   8^(c)  19   −37    10  −10^(c)   −55    Flashpoint, Tag 100    104    102    94   107    113   94   133    closed cup ° C. Physical Properties (typical values) Autoignition 370    375    360    365    365    360    365    >370    temp.,° C. Latent heat of 81   80   79   85   81   79   82   N/A vaporization,cal/g Viscosity at 25° C., 2.4 2.5 2.5 2.5 2.5 2.5 2.4 18.8  cst SolventProperties non-polar^(d) 8.3 8.3 8.3 8.3 8.3 8.3 8.3 7.9 polar^(d) 2.32.2 2.1 2.5 2.3 2.1 2.3 1.3 hydrogen bonding^(d) 4.8 4.7 4.5 5.0 4.8 4.54.8 3.6 Surface tension  3.56 N/A N/A N/A N/A N/A N/A 27.2 at 20° C.,dynes/cm Electrical 0.5 N/A N/A N/A N/A N/A N/A N/A Resistance^(e) at24° C., Meg Ohms^(a)Average for mixture^(b)Äsp. Gr./ÄT = −0.0007 per ° C. over the range 20-50° C.^(c)Approximate, based on composition^(d)Hansen Solubility Theory^(e)Ransberg Paint Resistance Tester Model 219CB^(f)Di-Isobutylester

Terpene and Isoprenoid Compositions

In yet another aspect, the invention relates, in part, to the novel useof either standard DBE or LVP-DBE in a polystyrene low heat treatmentextruder recycling system that can be more effective if mixed withterpenes or isopernoids such as, for example, and not by way oflimitation, d-limonene. In certain other embodiments, the polystyrenelow heat treatment extruder recycling system of the present inventioncan be utilized solely with one or more terpenes or one or moreisopernoids or any combination thereof.

In one embodiment, terpenes, isopernoids can be added and the additionof any from the family of non-ionic surfactants will serve to raise theflash point. A representative example of a non-ionic surfactant would beNP 9 or the terpenes such as d-limonene, etc. Other foam reducing agentssuch as esters from celery, or other vegetables such as soybean, etc.,or for example, olive oil, will work but prove to be inefficient ontheir own. In another embodiment, some of the above esters do not have alow flash point or have higher vapor pressure working in combinationwith LVP-DBE but will work in combination just as fast and in some caseeven at faster rates of reduction. In short, the addition of surfactantsserves to help raise the boiling point of other solvents. All of theother compositions in the terpenes and isoprenoids family have lowerboiling points compared to both standard DBE and or LVP-DBE.

The term “surfactant” is used following the nomenclature system of theInternational Cosmetic Ingredient Dictionary, 5.sup.th ed., J. A.Wenninger et al. eds., The Cosmetic, Toiletry, and FragranceAssociation, Washington, D.C. (1993), usually followed by a chemicalname and a trademark name of a particular product. Other non-limitingexamples of surfactants useful in the compositions and methods of thepresent invention are isotridecyl alcohol tri-ethoxylate (Surfonic™TDA-3B, Huntsman Corp.), C.sub.9-C.sub.11 pareth-6 [polyethylene glycolether of mixed synthetic C.sub.9-C.sub.11 fatty alcohols having anaverage of 6 moles of ethoxalate; Neodol™ 91.6], C.sub.11-C.sub.15pareth-59 [polyethylene glycol ether of mixed syntheticC.sub.11-C.sub.15 fatty alcohols having an average of 59 moles ofethoxalate; Tergitol™ 15-S-59], nonoxynol-6 [polyethylene glycol (6)nonylphenyl ether; Tergitol™ NP-6], nonoxynol-9 [polyethylene glycol (9)nonylphenyl ether; Tergitol™ NP-9], and a modified alkanolamidealkanolamine [Monamine™ 1255], as well as other surfactants known tothose of skill in the art.

Extruders and Thin Film Evaporators

In each of the aforementioned aspects and embodiments of the low heattreatment extruder methods of reducing polystyrene foam of the presentinvention, any form of extruder known to those of skill in the art maybe used, in combination with low heat, to reduce the volume ofpolystyrene foam. Non-limiting representative examples of extruders thatmay be used in the methods of the present invention include, inter alia,U.S. Pat. Nos. 5,490,725, 5,141,426, 5,125,824, 5,096,638, 5,089,193,5,064,587, 4,892,691, 4,615,664, 4,431,311, 4,201,480, 4,160,638, theentire contents of each of which are incorporated by reference in theirentirety.

The preferred extruders for use in the methods of the present inventioninclude those extruders for example as manufactured by BerstorffCorporation (Florence, Kentucky) and/or Hermann Berstorff MaschinenbauGmbH (Hannover, Del.). A non limiting representative example of aBerstorff Corporation extruder for use in the methods of the presentinvention is Model Number Twin Screw Extruder ZE-25.

Such extruders include, for example, and not by way of limitation,single extruders with varying bore sizes, twin extruders with varyingbore sizes, devolatilization extruder, devolatilizer screw and barrelarrangement, rear vent extruder, feed superheat extruder, and/or anycombination thereof. The varying bore sizes of the extruders used in themethods of the present invention are preferably on the order ofapproximately 25 mm to 128 mm. In certain embodiments, The bore size ofone or more large bore size extruders that may optionally be used in themethods of the present invention is the order of approximately 756 mm.

One example of a twin screw extruder that may be used in the low heattreatment extruder methods of the present invention is that described inExample 1, infra. Yet another of a twin screw extruder that may be usedin the low heat treatment extruder methods of the present invention isthat depicted in Example 2, infra.

In each of the aforementioned aspects and embodiments of the low heattreatment extruder methods of reducing polystyrene foam of the presentinvention, any form of thin film evaporator known to those of skill inthe art may optionally be used, in combination with low heat extruders,to reduce the volume of polystyrene foam. Such thin film evaporatorsinclude, for example, and not by way of limitation, the thin filmevaporator depicted in Example 1, infra.

In another embodiment, the polystyrene foam may be shredded or grindedprior to exposure to the specific esters combination using one or moreextruders of the present invention in combination with any othermechanical apparatus known to those of skill in the art for shredding orgrinding polystyrene foam and the aforementioned specific estercombination is then applied using a solvent spraying unit physicallyconnected to the mechanical apparatus. In this embodiment, a containermay be placed under the apparatus to collect the reduced sprayedpolystyrene foam.

In yet another embodiment, the polystyrene foam may be shredded orgrinded prior to exposure to the specific esters combination using anymechanical apparatus and the specific ester combination is then appliedusing a hand held solvent spraying unit.

Properties of the Recaptured Low Vapor Pressure Dibasic Ester (LVP-DBE)Composition

In each of the aforementioned aspects and embodiments, the resultanthigh quality beaded polystyrene product so produced has a heat index ofless than about 9. It is intended herein that the range implied within aheat index of less than 9 also includes all those specific recitations,including 9, 8, 7, etc., and any fraction thereof without actuallyreciting each specific range therewith.

In each of the aforementioned aspects and embodiments, the resultanthigh quality beaded polystyrene product so produced contains the dibasicesters, the low vapor pressure dibasic esters and/or the terpenes orisopernoids in a concentration of less than about 1-1000 ppm. It isintended herein that the range concentration of less than about 1-1000ppm also includes all those specific recitations, including 1, 2, 3- toabout 998, 999, 1000, etc., without actually reciting each specificrange therewith.

In each of the aforementioned aspects and embodiments, the resultanthigh quality beaded polystyrene product so produced contains no evidenceof spleaning, crazing or burnt discoloration. As used herein, the phraseno evidence of spleaning or crazing is commonly known to those of skillin the art of polystyrene that the beaded polystyrene end product willcontain no evidence of hairline fractures and/or cloudiness in the endproduct. As used herein, the phrase no evidence of burnt discolorationis commonly known to those of skill in the art of polystyrene that thebeaded polystyrene will contain no golden brownish or reddish color.

In each of the aforementioned aspects and embodiments, the resultanthigh quality beaded polystyrene product so produced has relatively lowmelt viscosity. As used herein, relatively low melt viscosity meansunder a load temperature of 450 degrees Farenheit.

Uses of the Recaptured Standard Dibasic Ester and/or Low Vapor PressureDibasic Ester (LVP-DBE) Compositions

In yet another aspect, the invention relates, in part, to the novel useof the recaptured Standard Dibasic Ester and/or LVP-DBE composition ofthe polystyrene low heat treatment extruder recycling system of thepresent invention as a paint stripper.

In yet another aspect, the invention relates, in part, to the novel useof the recaptured Standard Dibasic Ester and/or LVP-DBE composition ofthe polystyrene low heat treatment extruder recycling system of thepresent invention as a graffiti remover.

In yet another aspect, the invention relates, in part, to the novel useof the recaptured Standard Dibasic Ester and/or LVP-DBE composition ofthe polystyrene low heat treatment extruder recycling system of thepresent invention as a water proofing agent that may be applied viaspray means or brush on means.

In yet another aspect, the invention relates, in part, to the novel useof the recaptured Standard Dibasic Ester and/or LVP-DBE composition ofthe polystyrene low heat treatment extruder recycling system of thepresent invention for removing paints, inks, grease, and the like fromskin.

In yet another aspect, the invention relates, in part, to the novel useof the Standard Dibasic Ester and/or LVP-DBE composition of the presentinvention as an extender of the life of concrete by mixing in a minimumof 1.5% of the composition (the reduced polystyrene) but not to exceed27.5% of the composition.

In yet another aspect, the invention relates, in part, to the use of therecaptured Standard Dibasic Ester and/or LVP-DBE composition of thepolystyrene low heat treatment extruder recycling system of the presentinvention as an adhesive remover.

In yet another aspect, the invention relates, in part, to the novel useof the recaptured Standard Dibasic Ester and/or LVP-DBE composition ofthe polystyrene low heat treatment extruder recycling system of thepresent invention as a tar remover.

In yet another aspect, the invention relates, in part, to the novel useof the recaptured Standard Dibasic Ester and/or LVP-DBE composition ofthe polystyrene low heat treatment extruder recycling system of thepresent invention as a stain remover.

In yet another aspect, the invention relates, in part, to the novel useof the recaptured Standard Dibasic Ester and/or LVP-DBE composition ofthe polystyrene low heat treatment extruder recycling system of thepresent invention as a scuff mark remover.

In yet another aspect, the invention relates, in part, to the novel useof the recaptured LVP-DBE composition of the polystyrene low heattreatment extruder recycling system of the present invention as ageneral degreaser.

In each of the aforementioned aspects and embodiments, the resultanthigh quality beaded polystyrene product so produced by the novelpolystyrene low heat treatment extruder recycling system may beseparated from said solution so that the gel-like substance may beapplied externally to said object or mixed with said materials toincrease said object's or said material's waterproofing agent'scharacteristics, paint stripper's characteristics, graffiti remover'scharacteristics, extender of the life of concrete's characteristics,adhesive remover's, stain remover's characteristics, scuff markremover's characteristics, and/or general degreaser's characteristics,or any combination thereof, or increase the recycleability of thegel-like substance into polystyrene foam.

Methods of Reducing Polystyrene Foam Using the Low Heat TreatmentExtruder Recycling System

This invention solves the volume problem of polystyrene foam materialsand allows the easy and inexpensive shipment of the foam materials aftercost effective reduction in volume by use of certain liquid aliphaticdibasic esters. The materials used in the LVP-DBE composition comprisedimethyl glutarate, dimethyl adipate and dimethyl succinate (with theproviso that the dimethyl succinate is in weight percentage amounts of1% and less), which are effective foam reduction agents. While they haveactivity individually, as mixtures of dimethyl glutarate and dimethyladipate with dimethyl succinate in weight percentage amounts of 1% andless, the action is especially favorable. Moreover, with the addition ofsmall amounts of heat to the process, the overall effectiveness of theLVP-DBE composition is increased while having little effect on the costof recycling. In particular, when heat is added to the process the speedof reduction of the polystyrene foam or expanded polystyrene (EPS) isincreased. The heat can be introduced by several methods, for example,and not by way of limitation, heating the mixture by use of a drumheater or an inline heating element delivering the LVP-DBE or LVP-DBEmixture will dramatically the increase rate of reduction by up to three(3) to five (5)-fold but not to exceed twenty fold. Also, because of thelower boiling points of the individual reactants, very little reactantis lost in the heating process. The lower boiling points and benignnature of the reactants makes the reactant process safer than previouslyknown and commercially used chemical reactants with higher boilingpoints.

The use of the aforementioned active LVP-DBEs in the polystyrene lowheat treatment extruder recycling system of the present invention assistin making the expanded or foamed polystyrene materials easier to reduce,collapse and/or reprocess. The polystyrene foam bead or pumpable polygelproduct of this process is solvatable. The polystyrene foam bead productcan also be made pumpable and can then be filtered and reprocessed orinjected into furnaces where the high fuel value of the material offersconsiderable energy savings for users and/or recyclers. If filtered andrecycled, high quality polystyrene raw material bead product can bemade. In particular, both the standard DBE and LVP-DBE produce highquality beads. This is a function of the Styro Solve recycling systempreviously implemented by Katz et al., the contents of which arespecifically incorporated by reference in their entirety. By using theLVP-DBE of the present invention, the polygel so produced andtransported to the plant has proven to be more consistent than thatproduced using standard DBE. Since the LVP-DBE used in the methods ofthe present invention has a lower vapor pressure, it is noted that lessevaporation occurs on route to the processing plant and hence onereceives a more constant polygel product. This also translates into lesssolvent being used in the polystyrene reprocessing center. Moreover, byusing less solvent to produce the correct viscosity for recycling, onealso reduces the time and energy required in the process. This resultsin a more cost effective and cost efficient polystyrene foam recyclingprocess.

Heretofore, it has been impossible to cost effectively recyclepolystyrene high quality raw post consumer material. High qualityrecycling is important in polystyrene recycling where the recycledproduct is desirable to be used in the food packing industry. The foodpacking industry has strict requirements for parts per million ofcontaminants in the polystyrene used, the contents of which arespecifically incorporated by reference in their entirety. The processdisclosed herein is the only known recycling process that is both costeffective and yields recycled material that meets the requirements ofthe food packing industry while still satisfying the low vapor pressurecriteria established by the California Air Resources Board for volatileorganic compounds in consumer products per California Code ofRegulations, Title 17, Division 3, Chapter 1, Subchapter 8.5, Article 2,Section 94508(a) 80(A) and meets the exemption criteria for consumerproducts per EPA 40CFR59.203(f)1, the entire contents of which areincorporated herein by reference. The polystyrene low heat treatmentextruder recycling system of the present invention achieves these andother benefits as set forth herein.

Furthermore, the process of volume reduction of polystyrene foam hasbeen previously hampered by high loss due to evaporation. The use of thenovel composition of the present invention helps cure this problem byemploying polystyrene foam reduction agents comprising LVP-DBEs thatexhibit one or more of the following characteristics: (a) asignificantly lower vapor pressure than standard DBE, (b) thedistillation range of the solvent is narrower, (c) chemically morestable than standard DBE, (d) that is incompatible or can react with,inter alia, strong oxidizers, acids, alkalies, etc., (e) that will notundergo polymerization, (f) that reduces foamed or expanded polystyreneat a rate of action that equals or exceeds that of standard DBE, (g)that exhibits a greater holding capacity than standard DBE, (h) thatexhibits a higher flash point than standard DBE, (i) that has arelatively low odor compared to standard DBE; (j) that is not regulatedas a hazardous material by DOT, IMO, or IATA, and (k) for which none ofthe components present in the LVP-DBE composition are listed by IARC,NTP, OSHA or ACGIH as a carcinogen.

The materials used in this method of polystyrene foam volume reductionare also recoverable by removal in the recycling process and themajority of compounds used can be easily separated from moisture andvolatile organics by a combination of decanting, mutual solubility withother organic compounds and thermal stripping. The materials are furtherenvironmentally non-toxic.

The development of this invention began with identification of theunexpected affinity of the vapors of certain solvents found in perfumes.Identification of the active agent in the process became the key to theinitial polystyrene foam volume reduction process. This materialidentified was d-limonene. D-limonene vapors acted upon the polystyrenefoam and rapidly reduced the volume. The sorption process, when therewas sufficient vapor present, was one that continued until thepolystyrene foam was reduced to a viscous liquid. This aggressive mutualsolubility was relatively fast as long as there is a presence of theneeded vapors.

This invention furthers the concept of foam reduction by the furtherdiscovery of a set of chemicals which are as effective as the vaporprocess noted with d-limonene but which work in a liquid state and thusavoids the need for a vapor saturated atmosphere around the collapsingfoam. The inventor's prior work focused on the combined use of non-lowvapor pressure dimethyl glutarate and dimethyl adipate, and dimethylsuccinate (CAS# 119-40-0; CAS# 627-93-0; CAS# 106-65-0, respectively)which are effective polystyrene foam reduction agents. The presentinvention furthers this prior discovery in that one or more extrudersare used to grind the polystyrene foam in the presence of low heat.

The present invention also furthers this prior discovery in that one ormore mechanical extruders are used to grind the polystyrene foam in thepresence of low heat and one or more LVP-DBEs are employed as effectivepolystyrene foam reduction agents. In certain embodiments, the use ofdimethyl succinate (CAS# 106-65-0) in weight percentage amounts greaterthan 1% is specifically excluded from the scope of the claims of thepolystyrene low heat treatment extruder recycling system.

This invention discloses the new combination of chemicals in conjunctionwith low heat extruder processing of polystyrene foam and/or EPS thathave not previously been considered for this purpose since they are noteasy to use in the vapor phase. This new low vapor pressure dibasicester combination of dimethyl glutarate and dimethyl adipate withdimethyl succinate present in weight percentage amounts of 1% and lesseliminates much of the loss of the LVP-DBE reagents and further improvesfire safety of the recycling or foam reduction process. The extra factoris the removal of the vapor requirement with discovery of liquid phasefoam reduction agents. Importantly, by lowering the vapor pressure andlowering the loss of the LVP-DBE, the final stage of the reprocessing(recycling) is completed in a much more efficient manner. Moreimportantly, this new method of recycling polystyrene foam using LVP-DBEnow falls under the new California Code of Regulations, Title 17,Division 3, Chapter 1, Subchapter 8.5, Article 2, Section 94508 (a)80(A) vapor-pressure EPA standards, the entire contents of which areincorporated herein by reference, thereby allowing the product to beused whereas the current standard DBE can not. Also, as noted supra, useof the LVP-DBE allows the polygel to be more safely transported to therecycling plant since there is less vapor pressure and thus, lessevaporation of the LVP-DBE.

The formulas used for this invention consist of esters, specificallydibasic esters. These esters, especially the aliphatic dibasic esterssuch as dimethyl glutarate and dimethyl adipate (CAS# 119-40-0 and CAS#627-93-0, respectively) have rapid reaction with polystyrene foams (bothfoamed and expanded), again acting as a stress cracking agent to destroythe cell wall webs which are highly stressed, then destroying theintercellular structure that remains. In addition, throughexperimentation that is the subject of the invention disclosed herein itwas learned that the esters themselves were effective reactants whensmall amounts of heat were added to the process. Esters have beendisclosed in a U.S. patent to Shiino et al. U.S. Pat. No. 5,629,352.However, that disclosure does not teach nor contemplate heating. Theaddition of small amounts of heat to the LVP DBE ester composition ofthe present invention prior to its use as a reactant greatly increasesis reactant characteristics. The presence of esters without heat willreduce foam but in a time period that is not efficient for recyclingpurposes.

The dibasic or dialkyl esters disclosed herein for use in thepolystyrene low heat treatment extruder recycling system of the presentinvention are not like the vapor processes used previously for foamreduction, which attack polystyrene foam by dissolving the polystyrenefoam in the vapors of natural organic compounds. The present dibasicester chemicals act as liquids. The dibasic esters have boiling pointsof 196 to 225° C., with a vapor pressure of only 0.2 mm Hg at 20° C.while the vapor pressure for LVP-DBE is only 0.02 Hg® 20° C. They havean evaporation rate one tenth that of butyl acetate (Vapor pressure: 8mm Hg at 20° C.), a common reference. Should the evaporation read fromone fortieth for standard DBE (vapor pressure of 0.2 mm Hg @20° C.) andone four hundredth for LVP-DBE (vapor pressure of 0.02-0.04 mm Hg @ 20°C.). The specific gravity is slightly greater that water and mutualsolubility is limited, allowing easy separation from water mixes. Thedibasic esters also have low solubility in water and very highsolubility in many alcohols so that separation schemes for recovery ofthe dibasic mix is feasible. The use of the dibasic esters, especiallyas a mixture, eliminates the large loss due to evaporation of thed-limonene used as the reducing agent in previous polystyrene foamreduction and recovery methods. The evaporation of active agents hadpreviously made the process partly ineffective in many applicationsbecause of cost. The present invention is cost effective since this lossis very low.

The active agents also have several key property requirements or needs.Since the active agents will ultimately be placed into trash and garbagedumps, they must be environmentally safe and sound. Ideally, the activeagents should not be within a range of boiling points and vaporpressures that will either immediately flash off or will over timeevaporate to form a vapor layer within a landfill. With respect tosolvents, which attack polystyrene foams, nearly all solvents areenvironmental problem chemicals. One class of chemicals broadly noted asisoprenoid and terpene compounds contain mostly environmentally safenaturally derived compounds, but most of these compounds are relativelyvolatile and would at least form a vapor layer in a landfill dumpsituation. The dibasic esters of this invention are of sufficiently lowvolatility that they do not form an indump/landfill vapor layer. Thisremoves future problems of large vapor escape if the dump/landfill topimpermeable layers are destroyed or damaged by man made or naturalphenomena such as, inter alia, earthquakes.

In the prior patents on activation (for example, U.S. Pat. No.5,223,543) the emphasis was on d-limonene. This reduction agent wasselected for cost and volatility reasons since prior uses in the fieldrelied on rapid action due to application in exposed areas as activatedliquid. The use of a variety of liquid volatilities as long as vapor isgenerated over an extended time ranging from several hours to severaldays is also contemplated herein. The present use of esters with smallamounts of heat, dibasic esters, and d-limonene in combination withesters and dibasic esters, as foam reduction agents is also effectiveand is specifically contemplated herein. The present invention is vastlysuperior compared to the use of standard DBE in creating a vastreduction in the vapor loss, in preventing vapor layers within garbageor landfill disposal dumps, in reduction of loss in reprocessingoperations, which are typically at temperatures of over 270° C. Also,the present invention limits reliance on d-limonene, which canexperience unstable pricing and is not easily reclaimed after recycling.

Finally, all of the contemplated reactants described herein may beoptionally aided in their reactant effectiveness by including in thereactant process a pretreatment shredding or grinding of thepolystyrene. The shredding can be effectively accomplished through theuse of a hopper that shreds the polystyrene in the first stage of theprocess. The second stage of the process would have the shreddedpolystyrene being treaded with one of the disclosed reactants in aholding compartment of the hopper. The resultant foam sludge could thenbe pumped from the hopper to containers for transportation to waste orrecycling locations.

In one embodiment, a mixture of a dibasic esters comprising dimethylglutarate, dimethyl adipate, and dimethyl succinate with the dimethylsuccinate being present in weight percentage amounts of 1% and less; anda surfactant, are sprayed onto pre-shredded polystyrene foam waste. Inanother embodiment, a mixture of a dibasic esters comprising dimethylglutarate, dimethyl adipate, and dimethyl succinate with the dimethylsuccinate being present in weight percentage amounts of 1% and less, aresprayed onto pre-shredded polystyrene foam waste in the absence of asurfactant.

Types of Polystyrene Foam and/or Expanded Polystyrene Foam that May beReduced Using the Low Heat Extruder Methods

Examples of foam waste that can be reduced using the compositions andmethods of the present invention can be from a variety of sources thatinclude, for example, and not by way of limitation, foam serving platesand containers in a fast food restaurant, the residues of packing forfood or industrial objects (representative non-limiting examples offoamed or expanded polystyrene that can be reduced using the methods ofthe present invention include, inter alia, computer end caps, packagingexpanded polystyrene (EPS) peanuts, insulation board, Styrofoam®,construction forms, coffee cups, egg cartons, drink cups, meat trays,vegetable trays, protective packaging, furniture, lamps, lamp shades,paintings, appliances such as refrigerators, stove dish washers,microwave ovens, cameras, VCRs, TVs, telephones, vacuums, radios,chemical packaging military applications for pollution prevention itemssuch as: munitions packaging, target drones, weapons, food service,agriculture; seedling trays, various industries such as tobacco growers,greenhouses (for their seeding trays) plant growers for their planting,fruit and vegetable growers for their shipping containers; foam coolers,fish containers, among others. The foam waste would be shredded in ahopper. The shreds of polystyrene foam would be contained in acompartment of the hopper. The reactant would be sprayed onto theshredded foam waste. The spray and shredded foam combination willrapidly decrease in volume as the foam collapses and would result in theforming of foam sludge and volume of reducing agent. The sludge andreducing agent would be pumped from the hopper compartment into drumtype containers and sent to dumps where it occupies a greatly reducedvolume or sent to a reprocessor to recover the active agent dibasicesters and the polystyrene polymer. Preferably the reducing agent isninety percent dibasic ester and not to exceed 10 percent surfactant.

The process is preferably the same as described above with alternatereactant compositions. However, the embodiments contemplated herein arenot limited to the pre shredding of the foam waste, the use of a hopper,the pumping of the foam sludge and reactant or the use of drum-likecontainers for transporting the foam sludge and reactant. Indeed, theembodiments contemplated herein may be used in conjunction with otherprocessing methods of polystyrene foam waste known to those of skill inthe art.

In a second embodiment, the reactant is at least one of the three nameddibasic esters which is combined with d-limonene; and a surfactant,whereby the reactant in a liquid state contacts polystyrene foam causingthe collapse of the polystyrene cell to form a compact polystyrene gelmaterial that is easily shippable. Preferably the reactant, or foamreduction agent, is eighty eight weight percent of the dibasic ester,ten percent d-limonene and two percent of the surfactant. In addition,it is preferred that the surfactant is at least one of an industrystandard surfactant known as NP5 and NP9. Other non-ionic surfactantsknow to those of skill in the art can be used in conjunction with theDBE and LVP-DBE compositions of the present invention.

In a third embodiment, the reactant is a dibasic esters that is at leastone of the group of dimethyl glutarate, dimethyl adipate, and dimethylsuccinate, with the dimethyl succinate being present in weightpercentage amounts of 1% and less; d-limonene; and, a vegetable oil areused as the reducing agent whereby the reactant in a liquid statecontacts the polystyrene foam causing the collapse of the polystyrenecell to form a compact polystyrene gel material that is shippable.Preferably, the reactant, or foam reduction agent, is fifty five percentvegetable oil, thirty percent dibasic ester and fifteen percentd-limonene. It is also preferred that the vegetable oil is soy oil.Other examples of preferred oils include, for example, and not by way oflimitation, oils from celery and olives.

All of the embodiments described above are sprayed onto polystyrenefoam. The preferred process is to have the polystyrene foam placed intoa hopper wherein the foam is converted to small pieces that can becombined with the reducing agent. The resulting material, sludge andreducing agent are pumped from the hopper to drums for transportation.

EXAMPLES

It will be understood by one of ordinary skill in the relevant arts thatother suitable modifications and adaptations to the methods andapplications described herein are readily apparent from the descriptionof the invention contained herein in view of information known to theordinarily skilled artisan, and may be made without departing from thescope of the invention or any embodiment thereof. Having now describedthe present invention in detail, the same will be more clearlyunderstood by reference to the following examples, which are includedherewith for purposes of illustration only and are not intended to belimiting of the invention.

The embodiments described herein are not a limitation to inventiondisclosed by this application but are shown to illustrate the bestmethods and uses of the invention. Further uses would be obvious tothose skilled in the art by a complete review of the disclosure madeherein.

Example 1

Abstract

The objective of this experiment was to demonstrate the capacity of acounter rotating, non-intermeshing, twin screw extruder fordevolatilization of recovered polystyrene from dimethyl succinatesolvent. The feed to the devolatilizing extruder consisted of a syrupprepared by dissolving polystyrene foam in dimethyl succinate to 50%solids solutions. The devolatilization goal was less than 1,000 ppmdimethyl succinate residuals; with minimal degradation of thepolystyrene.

Introduction

Devolatilization is the thermodynamically driven removal of a solventfrom a polymer solution. When the amount of solvent to be removed is asignificant fraction of the solution, the devolatilization is mostefficiently performed in a staged separator. A staged, non-intermeshing,twin screw extruder has many characteristics which attract it to thedevolatilization process.

The non-intermeshing geometry has inherently more volume in the screwchannels than intermeshing designs of the same screw diameter. Byrotating the screws counter currently, the vent opening can extend aboveand beyond the center line of both screws. The downward motion of bothscrews in the apex conveys material away from the vent opening andforward to the next melt seal. The vent opening can be as long as 8screw diameters, which results in a generous area for vapor flow, withcorrespondingly low vapor velocity and particle entrainment.

The rate of devolatilization for a concentrated polymer solution islargely controlled by molecular diffusion of the solvent through thepolymer. The diffusion rate is determined by residence time and theconcentration gradient in the melt, which is in turn determined by thesurface area renewal rate and vapor pressure above the melt. The rate ofsurface area renewal is enhanced in counter rotating, non-intermeshingtwin screw extruders by the exchange of material from one screw to theother, resulting in good distributive mixing. It is also possible toincrease the surface area in the melt by injection of a stripping agentunder pressure, which foams the melt on contact. An additional benefitof injecting a stripping agent is the reduction of solvent vaporpressure above the melt, which increases the driving force fordevolatilization.

Materials and Methods

Equipment and Feed Materials

Extruder:

The 30 mm devolatilizing extruder arrangement featured a WeldingEngineers model HTR-30 mm-22-1 V2-2-3-13-E1 twin screw extruder. Thetotal length of the extruder consisted of 54:1 L/D twin screw plus a 6:1L/D single screw discharge. A process schematic for the extruderconfiguration is shown in FIG. 1.

Extruder Heating:

The 30 mm devolatilizing extruder was heated with hot oil circulatedthrough the barrels, which were cored or jacketed. One zone of hot oilwas used for all of the barrels.

Feed Equipment:

The feed system for the devolatilizing extruder consisted of a Zenith 11cc/rev gear pump downstream of a pressurized, 50 gallon Pfaudlerjacketed kettle, feeding into the second barrel on the extruder.Nitrogen was used to pressurize the kettle. A Koch SMR heat exchangerwith 6 ft² of area was used to preheat the feed, and was positionedupstream of a solution feed valve installed on the second barrel. Thefeed kettle, heat exchanger, and pipe heat tracing were heated with hotoil to allow control of the feed temperature.

Solvent Recovery System:

Vapors from the rear vent were condensed in a 21 ft² shell and tube heatexchanger mounted upstream of a 30 gallon kettle.

A Nash model AHF120 liquid ring pump with 100 SCFM capacity was used forthe rear vent and first downstream vent of the 30 mm extruder. Initiallypure water, then collected dimethyl succinate, was used as the sealfluid in the pump. A 16 ft² shell and tube heat exchanger was used as acondenser between the vent stack and the Nash pump, with plant coolingwater on the shell side.

Two Stokes Microvac model 148-10 oil-sealed pumps with 50 SCFM capacitywere used on the two final downstream vents. 1 ft² shell and tube heatexchangers were used as condensers between the second and thirddownstream vent stacks and the corresponding collectors, with plantcooling water on the shell side.

The vacuum level in all vents was measured by dial gauges.

Materials:

The following feed materials were used, and are designated by theirrespective letter codes in the experimental run summary in Section VII,and the operator log sheets in Section IX.

A. Recovered polystyrene in dimethyl succinate, approximately 50%solids.

Experimental Procedure

For each days run of the devolatilization extruder, the 50 gallon feedkettle was filled with syrup supplied in a 55 gallon drum. The syrup hadto be filtered to remove undissolved polymer by pouring it through ascreen into 5 gallon buckets, which were then poured into the kettle.

The extruder screw and barrel arrangement 961841_(—)1, shown in FIG. 2,used a rear vent and three downstream vents to remove the solvent. Therear vent was operated with slight vacuum drawn off the Nash pump. Themaximum vacuum that the pumps could develop was used in the downstreamvents. The product was collected by extruding through a two hole stranddie into a water bath, and then pelletized. A day by day description ofthe trial now follows.

Day 1

On the first run day of the trial, a lot of time was spent filtering thesyrup to charge the 50 gallon kettle. There was a lot of undissolvedpolymer in the syrup that looked like pieces of plastic bags. When thekettle became mostly full of syrup, the extruder was started up to checkthe operation of the feed and vacuum systems.

When the extruder was first started, the vacuum pump for vent 3 spewedoil because it was dead headed and not primed. The system was shut downto check operation of the vacuum pump, then restarted at a relativelylow rate. The extruder was run for about 20 minutes with the vents clearand the temperatures stabilized, then sample 1 was collected at 19.4lb/hr product rate and 244 rpm screw speed. The screw speed wasincreased to 400 rpm for sample 2, then the rate was increased to 32.2lb/hr for sample 3. The rate was increased further to 40.1 lb/hr forsample 4, before shutting down the process to fix some problemsexperienced with the vacuum system.

During the run the vacuum level in vent 3 was always worse thanexpected, and no solvent was collected off the rear vent, because thefeed temperature was too low. The vent 3 vacuum pump oil was changed,and it was discovered that a large amount of solvent was collected offvent 4. These factors combined indicate that samples 1 through 4 shouldhave high residuals, because of poor utilization of the upstream vents.

Day 2

On the second day of the trial, the extruder was started up with higherfeed and barrel temperatures, which resulted in solvent being recoveredoff the rear vent. After start up, poor vacuum was again seen in thethird vent. Further investigation revealed the vent 3 condenser wasclogged with polymer, which when replaced with a clear condenser allowedfor strong vacuum in the third vent.

The extruder was started up at a low rate of 12 lb/hr at 215 rpm, toallow time for the feed temperature to gradually increased above 200°C., at which temperature the rear vent started to work. This was alsodone to conserve material, since the second drum of syrup shipped forthe trial was too dirty to screen effectively. All of the samples inthis trial were taken from the initial drum of feed that was supplied.

Sample 5 was taken at the low rate condition, then the rate wasincreased to 18.7 lb/hr and the screw speed increased to 300 rpm forsample 6. The screw speed was increased to 400 rpm for sample 7, thenthe rate was increased to 27.6 lb/hr for sample 8. The next threesamples were collected at 31.9 lb/hr, 37 lb/hr, and 41.3 lb/hr; all at ascrew speed of 400 rpm. For sample 12 the screw speed was increased to500 rpm, then the rate was increased to 55 lb/hr, before increasing tothe maximum rate of 83.2 lb/hr for sample 14.

At the maximum rate of 83.2 lb/hr at 500 rpm, the screw channels in thedownstream vents were seen to be full of melt. Increasing the ratefurther would have caused melt to flood one or more vent stacks. Shortlyafter sample 14 was taken, the feed kettle was depleted, and theextruder was shutdown, thus ending the experimental part of the trial.

Results and Discussion

A summary of the run conditions for the samples collected is given inSection VII. A copy of the operator log sheets is given in Section IX.This trial was successful in identifying rate and product performancespecifications for devolatilization of recycled polystyrene foam fromdimethyl succinate. Sufficient data was collected to design commercialscale extruders for this process.

The devolatilization performance can be evaluated in terms of rear ventperformance, screw design and specific rate, residual solvent levels,melt temperatures, and melt flow index.

Rear Vent Performance

Rear vent flow rates were not measured in this test, because the rearvent collector was operated under slight vacuum. During the first runday, little if any solvent was taken off the rear vent, because the feedtemperature was too low. During the last run day, the higher feedtemperatures used resulted in some solvent entering the rear ventcollector.

Typically, dilute solution (˜50% solids feed) devol extruders reachmaximum capacity at rear vent yields around 60%. However, since dimethylsuccinate has a high boiling point, the feed temperature must be quitehigh to achieve high rear vent yields. This is because the rear vent isan adiabatic flash separation stage, and the yield off the rear vent isa function of both the feed superheat and extruder pumping capacity.FIG. 3 is a plot of rear vent yield as a function of feed superheat,calculated from an adiabatic flash, where the feed superheat was definedas the difference between the partial pressure of dimethyl succinate inthe feed, and the rear vent pressure. Flory-Huggins thermodynamics wasused to calculate the partial pressure of dimethyl succinate at themeasured temperature and concentration of the feed.

The adiabatic flash calculation shown in FIG. 3 indicates that rear ventyields were half or less the desired value of 60%. This was because thefeed temperature was low, even at 215° C. Note that there were somesample conditions with calculated negative feed superheats. Thesecorrespond to the samples run the first day, were the feed temperaturewas below the equilibrium boiling point of the dimethyl succinate,resulting in no solvent off the rear vent. Although the points in FIG. 3are calculated from a model, the scatter in the results is because themeasured feed superheats are relatively low, which caused the computercode to perform a lot of iterations to find the proper solution.

The maximum amount of solvent that can be removed from the rear ventwill set a volumetric rate limitation for the extruder. Typically for a30 mm extruder at specific feed rates of 0.2 lb/hr/rpm and above, therear vent yield will drop off because the rear vent becomesvolumetrically limited. Normally when this occurs, foam will fill eitherthe rear vent or first downstream vent stack, as more solvent is passeddownstream. Samples 4, 11, and 13 had specific feed rates around 0.2lb/hr/rpm; and sample 14 had a specific feed rate of 0.33 lb/hr/rpm.However, both the rear vent and first downstream vent appeared wellbehaved for those samples. It is not desirable to operate adevolatilization extruder at low rear vent yields, because a lot ofsolvent is passed to the downstream vents and vacuum system, and theproduct residuals will be high.

Effects of Screw Design and Specific Rate

Only one screw design was tested in this trial. The screw design (seeFIG. 2) featured scaled conveying elements in the rear vent, and meltseal cylinder sizes, that have proved successful in 6″ devolatilizationextruders processing styrenic copolymers at product rates up to 3ton/hr.

The specific energy as a function of specific rate is plotted in FIG. 4.Specific energy decreases with increasing specific rate, because theextruder becomes a more efficient pump as it becomes more full. Thiscurve can be scaled up and used to determine the power consumption andmotor size of commercial size extruders, as discussed in Section E ofExample 1. The specific energies measured in this trial are low relativeto what Welding Engineers' typically measure for devolatilizationextruders. This indicates the recycled polystyrene processed hadrelatively low melt viscosity and molecular weight, two desirableproperties of the methods employed herein.

Residual solvent levels usually correlate to specific rate, with lowerresiduals corresponding to lower specific rate. In this trial, thesamples that were analyzed for residual solvent level had all less than1 ppm dimethyl succinate. No trend could be seen in the data because thevalues were so low. This result was unexpected, however the samples wereanalyzed by the customer using GC and FTIR methods, and are believed tobe accurate.

Effects of Melt Temperatures

Since extruder devolatilization is mostly mass transfer limited, thereis usually an influence of melt temperature on the residuals. Lowerresiduals are the result of higher melt temperatures. The melttemperature profile is determined by screw design, screw speed, andrate. The influence of barrel temperature is significant at 30 mm scale,but becomes less so as extruder size increases.

In this trial, the variable that most determined the melt temperatureswas the specific rate, as shown in FIG. 5. The scatter was due to theindependent affects of screw speed and rate on melt temperature, becausesamples were taken over a range of screw speeds from 215 to 500 RPM. Ingeneral, higher rates at a constant screw speed result in lower melttemperatures, because the screw channels are more full and the meltexperiences less overall shear. With high viscosity polymers, screwspeed becomes the dominant variable that determines the melt temperatureprofile.

For polymers which can degrade or depolymerize, there exists a maximummelt temperature that the material can withstand in an extruder. Styrenemonomer will depolymerize from styrenic polymers at temperatures near300° C. The screw design can be adjusted to maintain the maximumpermissible melt temperature by changing the diameter of the cylindricalmelt seal elements.

Product Degradation and Melt Flow Index

Product degradation was quantified in this trial by measuring the meltflow index. It is expected that higher temperatures and shear wouldcontribute to more degradation, and therefore higher melt flow indexvalues. However, no significant degradation was measured by the customerfor any of the samples collected in this trial.

Scale Up Considerations for Devolatilization

The rate and residuals achievable on a production size extruder can beestimated from scaling up the results of this trial. As extruder sizeincreases, the volume and conveying capacity goes up with the cube ofdiameter, while the area for heat and mass transfer goes up with thesquare of diameter. Vent pressure and feed temperature are used tocontrol rear vent yield and/or vapor velocity on commercial scaleextruders.

As seen in FIG. 3, the rear vent yield depended on the feed superheat,as long as the rear vent was not volumetrically limited. Ideally, theextruder should reach maximum capacity at about 60% yield in the rearvent, and 30 to 40% yield in the first downstream vent. This typicallyrequires a feed superheat of about 200 psi, which is achieved bypreheating the feed. In this trial, the highest feed superheats wereabout 40 psi, which is why the rear vent was under utilized. The feedtemperature needed for 200 psi superheat depends on the concentrationand vapor pressure of solvent in the feed.

The data in Section VII show that to achieve less than 1 ppm residualson a 30 mm extruder, specific rates about 0.1 lb/hr/RPM are sufficient.From FIG. 4, the specific energy consumption at 0.1 lb/hr/RPM is 0.08Hp-hr/lb, which is less than the typical value for existing commercialstyrenic polymer devol extruders. Based on a 2.5 scaling exponent forscrew diameter ratio, the following table of maximum capacity at <1 ppmresiduals, and power consumption at 500 rpm, versus extruder size, canbe constructed: Extruder Size (inch) Rate (lb/hr) at 1 ppm PowerConsumption (Hp) 2.0 187 18 2.8 433 46

It is expected that higher feed superheat will allow for higher capacitythan projected above, because of improved utilization of the rear vent.

Conclusions

This trial demonstrated the capacity of a non-intermeshing, twin screwextruder to devolatilize dimethyl succinate from recycled foampolystyrene. All the samples analyzed by the customer to date had lessthan 1 ppm dimethyl succinate residuals, which was well below thecustomer's goal of less than 1,000 ppm. The results show that a 2.8″extruder will be required to devolatilize to less than 1 ppm, at aproduction rate of over 400 lb/hr solids. It is expected that higherfeed temperatures than tested in this trial will allow for highercapacity.

Melt temperatures were determined by barrel temperatures, specific rate,and screw speed. It is possible to optimize the melt temperature profilein a commercial devol extruder through screw design changes.

Product degradation, as determined by melt flow index, was found to beinsignificant for the samples collected. Further testing of the sampleswill be required to quantify the effects that shear rate and temperaturehad on any degradation of the recovered polystyrene.

Experimental Run Summary Recycled Polystrene Devor Vent PerformanceData: Specific Vent 2 Vent 3 Vent 4 Product Feed Screw Drive RateSpecific Solvent Rear Vent Press. Press. Press % PS in Rate Rate SpeedCurrent (lb/hr/ Energy Residuals Press (mm (mm (mm Date Time Sample FEED(lb/hr) ((lb/hr) (RPM) (Amps) RPM) (HP − hr/lb) (ppm) (mm Hg) Hg) Hg)Hg) Day 1 15:38 1 50 19.4 38.8 244 5.0 0.080 0.081 — 519 76 152 13 15:492 50 19.2 38.4 400 5.0 0.048 0.134 <1 545 89 177 13 16:00 3 50 32.2 64.4400 4.0 0.081 0.064 — 583 101 177 13 16:11 4 50 40.1 80.2 400 3.0 0.1000.039 <1 583 165 253 13 Day 2 11:26 5 50 12 24.0 215 5.0 0.056 0.116 —659 76 <13 13 11:51 6 50 18.7 37.4 300 6.0 0.062 0.124 <1 659 63 <13 1312.05 7 50 18.4 36.8 400 6.0 0.046 0.168 — 659 76 <13 13 12:19 8 50 27.655.2 400 6.0 0.069 0.112 <1 671 76 <13 13 12:27 9 50 31.9 63.8 400 6.00.080 0.097 — 671 76 <13 13 12:39 10 50 37 74.0 400 6.0 0.093 0.084 <1671 76 <13 13 12:48 11 50 41.3 82.6 400 6.0 0.103 0.075 — 684 76 <13 1313:00 12 50 40.6 81.2 500 6.0 0.081 0.095 <1 671 76 <13 13 13:09 13 5055 110.0 500 6.0 0.110 0.070 — 684 76 <13 13 13:22 14 50 83.2 166.4 5005.5 0.166 0.043 — 684 76 <13 13 Process Temperatures and Pressures: HXInlet HX Out Feed Rear Vent Barrel 3 Vent 2 Barrel 5 Barrel 7 Die HotOil Setpoints Temp. Temp. Temp. Temp. Temp. Temp. Temp. Temp. Die Temp.Press. Koch Hx Extruder Day Time Sample (° C.) (° C.) (° C.) (° C.) (°C.) (° C.) (° C.) (° C.) (° C.) (psig) (° C.) (° C.) Day 1 15:38 1 61.7192.4 180.6 194.1 186.3 163.3 186.1 191.8 163.3 52 221 221 15:49 2 59.8192.6 181.2 194.7 185.9 164.6 188.9 198.3 165.3 53 221 221 16:00 3 58.8190.5 186.9 195.5 186.5 167.1 183.3 186.2 170.0 39 221 221 16:11 4 58.5188.9 186.4 195.7 186.9 167.2 182.7 183.6 168.1 24 221 221 Day 2 11:26 576.6 217.7 185.3 228.3 218.3 205.0 229.7 233.3 199.0 27 260 260 11:51 663.6 223.1 209.4 228.9 217.8 191.4 228.6 241.2 203.1 29 260 260 12.05 765.5 223.7 210.8 229.2 218.4 194.0 231.5 247.4 204.5 29 260 260 12:19 868.0 223.6 216.8 229.3 218.2 183.8 225.5 244.9 205.7 31 260 260 12:27 969.4 222.3 217.7 229.3 218.1 180.8 221.4 242.0 205.8 32 260 260 12:39 1071.3 219.7 216.7 228.4 218.0 177.5 216.5 237.0 203.9 35 260 260 12:48 1173.7 218.0 216.3 228.5 217.8 175.0 213.4 233.5 203.9 36 260 260 13:00 1277.1 217.5 215.9 228.7 217.5 175.5 215.8 239.7 205.3 33 260 260 13:09 1380.2 211.7 213.4 228.4 217.7 170.5 207.5 227.9 205.4 42 260 260 13:22 1485.0 204.0 205.9 227.5 216.3 167.3 197.4 204.5 201.7 38 260 260Adiabatic Feed Flash Specific Koch Heat Log SuperHeat Rear Vent FeedRate Transferred Mean Koch Uo Day Time Sample (PSI) Yield (%)(lb/hr/RPM) (BTU/hr) DT (° F.) (BTU/hr/ft2) Day 1 15:38 1 −3.0 0 0.1594475 137 5.4 15:49 2 −4.2 0 0.096 4497 138 5.4 16:00 3 −0.8 0 0.161 7482142 8.8 16:11 4 −1.3 0 0.201 9224 145 10.6 Day 2 11:26 5 −7.7 0 0.1122989 173 2.9 11:51 6 27.5 13 0.125 5261 172 5.1 12.05 7 30.2 19 0.0925135 170 5.0 12:19 8 42.0 26 0.138 7576 169 7.5 12:27 9 44.1 27 0.1608600 170 8.4 12:39 10 41.7 20 0.185 9684 173 9.3 12:48 11 40.1 24 0.20710513 174 10.1 13:00 12 39.9 23 0.162 10059 173 9.7 13:09 13 33.8 160.220 12765 180 11.8 13:22 14 19.4 9 0.333 17470 188 15.5

TABLE 3 SCREW VACUUM PRODUCT HOT OIL SPEED INCHES RATE DIE PROD. FOODTIME FEED SCREWS R.P.M. AMPERES 1 2 3 #/HR. SAMPLE DIE PSIO TEMP. ZONE 1° C. 2:37 Start-up - turn on feed pump - low speed 2.30 3:00 Shut down -states pump on vent 3 flooded; Rear vent has material in it 3:20Start-up again - vacuum on rear vent 3:25 at 2.0 feed pump, 244 adjustrpm 3:38 A 1 244 5 19.4 1 A 2.30 3:40 Raise screw speed to 357 rpm 3:49A 1 400 5 19.2 2 A 2.30 3:51 Raise rate, gear pump to 3.0, Poor vacuumvent 7 4:00 A 1 400 4 32.2 3 A 2.30 4:05 Rate at 3.5 set point; Nearlimit of vent flow in vent 3; Melt forms in vent 4, Temperatures toolow. 4:11 A 1 400 3 40.1 4 A 2.30 4:17 Shut down - turn off gear pump,empty extender, cool, close extender and leave. FEATURED ZENITH VACUUMLEVELS ZONE 2 PUMP 3 Vent 1 Vent 2 Vent 3 Vent 4 TIME ° C. Set-up 4 mmHg5 mmHg 6 mmHg 7 mmHg 8 2:37 2.30 3:00 Shut down - states pump on vent 3flooded; Rear vent has material in it 3:20 Start-up again - 1.1 vacuumon rear vent 3:25 at 2.0 feed pump, 244 adjust rpm 3:38 2.30 2.0 9.527   24 29.5 ¹ 3:40 Raise screw speed to 357 rpm 3:49 2.30 2.0 8.5 26.523 29.5 3:51 Raise rate, gear pump to 3.0, Poor vacuum vent 7 4:00 2.303.0 7.0 26.0 23 29.5 ² 4:05 Rate at 3.5 set point; Near limit of ventflow in vent 3; Melt forms in vent 4, Temperatures too low. 4:11 2.303.5 7.0 23.5 20 29.5 ³ 4:17

TABLE 4 SCREW VACUUM PRODUCT SPEED INCHES RATE DIE TIME FEED SCREWSR.P.M. AMPERES 1 2 3 #/HR. SAMPLE DIE PSIO 11:00 Start-up highertemperatures 11:15 At 1.0 gear pump setting, 187 rpm; replacing vent 3condense - original one way was plugged, causing poor vacuum before11:26 A 1 215 5 12    5 A 11:27 Raise screw speed to 300, rate to 2.00setting 11:51 A 1 300 6 18.7  6 A 11:52 Raise screw speed to 400 rpm12:05 A 1 400 6 18.4  7 A 12:06 Raise rate to 3.0 12:17 A 1 400 6 27.6 8 A 12:19 Raise rate to 3.5 12:27 A 1 400 6 31.9  9 A 12:29 Raise rateto 4.0 - venting o.k. 12:39 A 1 400 6 37.0 10 A 12:39 Raise rate to 4.512:48 A 1 400 6 41.3 11 A 12:50 Raise screw speed to 500 rpm  1:00 A 1500 6 40.6 12 A  1:01 Raise rate to 6.0  1:09 A 1 500 6 55.0 15 A  1:09Push rate, final limit - 8.5 set point = 81.6 16/11(12     rate)  1:22 A1 500 5-6 83.2 14 A  1:26 Shut down HOT OIL FOOD FEATURED ZENITH VACUUMLEVELS PROD. ZONE 1 ZONE 2 PUMP 3 Vent 1 Vent 2 Vent 3 Vent 4 TIME TEMP.° C. ° C. Set-up 4 mmHg 5 mmHg 6 mmHg 7 mmHg 8 11:00 /260 /260 11:15 At1.0 gear pump setting, 187 rpm; replacing vent 3 condense - original oneway was plugged, causing poor vacuum before 11:26 2.60 2.60 1.5 4 27 3029.5 11:27 Raise screw speed to 300, rate to 2.00 setting 11:51 2.602.60 2.0 4 27 30 29.5 11:52 Raise screw speed to 400 rpm 12:05 2.60 2.602.0 4 27 30 29.5 12:06 Raise rate to 3.0 12:17 2.60 2.60 3.0 3.5 27 3029.5 12:19 Raise rate to 3.5 12:27 2.60 2.60 3.5 3.5 27 30 29.5 12:29Raise rate to 4.0 - venting o.k. 12:39 2.60 2.60 4.0 3.5 27 30 29.512:39 Raise rate to 4.5 12:48 2.60 2.60 4.5 3.0 27 30 29.5 12:50 Raisescrew speed to 500 rpm  1:00 2.60 2.60 4.5 3.5 27 30 29.5  1:01 Raiserate to 6.0  1:09 2.60 2.60 6.0 3.0 27 30 29.5  1:09 Push rate, finallimit - 8.5 set point = 81.6 16/11(12     rate)  1:22 2.60 2.62 8.5 3.027 30 29.5  1:26¹ Five Minute rate check² Solvent collecting in wash³ Poor vacuum, low temperatures = high pp

Example 2

Determination of the Exposure Limits of the Recaptured LVP-DBEComposition of the Polystyrene Low Heat Treatment Extruder RecyclingSystem

Exposure Limits

DBE-LVP

PEL (OSHA): None Established

TLV (ACGIH): None Established

AEL*: 1.5 ppm, 10 mg/m3, 8 Hr. TWA

* AEL is DuPont Chemical Inc.'s Acceptable Exposure Limit. Wheregovernmentally imposed occupational exposure limits which are lower thanthe AEL are in effect, such limits shall take precedence.

Example 3

Determination of the Physical and Chemical Properties of the RecapturedLVP-DBE Composition of the Polystyrene Low Heat Treatment ExtruderRecycling System

Physical and Chemical Properties

Odor: Sweet

Form: Liquid

Specific Gravity: 1.1 @ 20 C (68)

Boiling Point: 210-225 C (410-437 F)

Vapor Pressure: 0.02-0.04 mm Hg @ 20 C (68 F)

Melting Point: −13 to 8 C (9-46 F)

% Volatiles: 100 WT % @ 20 C (68 F)

Evaporation Rate: <0.1 (Butyl Acetate=1.0)

Solubility in Water: 2.5-4.2 WT % @ 20 C (68 F)

Example 4

Determination of the Exposure Guidelines of the Recaptured LVP-DBEComposition of the Polystyrene Low Heat Treatment Extruder RecyclingSystem

Exposure Guidelines

Exposure Limits

DBE-LVP

PEL (OSHA): None Established

TLV (ACGIH): None Established

AEL *: 1.5 ppm, 10 mg/m3, 8 Hr. TWA

This limit is for DBE.

* AEL is DuPont's Acceptable Exposure Limit. Where governmentallyimposed occupational exposure limits which are lower than the AEL are ineffect, such limits shall take precedence.

Example 5

Determination of the Hazardous Chemical Indicators of the RecapturedLVP-DBE Composition of the Polystyrene Low Heat Treatment ExtruderRecycling System

Hazardous Chemical Lists

SARA Extremely Hazardous Substance: No

CERCLA Hazardous Substance: No

SARA Toxic Chemical: No

DBE-LVP is considered 100% VOC (1080 g/l) per EPA 40 C.F.R. Section51.100(s)1.

DBE-LVP meets the VOC exemption criteria for consumer products per EPA40 C.F.R. Section 59.203(f)1.

DBE-LVP meets the low vapor pressure (LVP) criteria established by theCalifornia Air Resources Board for volatile organic compounds inconsumer products per California Code of Regulations, Title 17, Division3, Chapter 1, Subchapter 8.5, Article 2, Section 94508(a)80(A).

Canadian Regulations

CLASS D Division 2 Subdivision B—Toxic Material. Skin or Eye Irritant.

Equivalents

The invention illustratively described herein suitably may be practicedin the absence of any element or elements, limitation or limitationswhich is not specifically disclosed herein. Thus, for example, in eachinstance herein any of the terms “comprising,” “consisting essentiallyof,” and “consisting of” may be replaced with either of the other twoterms. The terms and expressions that have been employed are used asterms of description and not of limitation, and there is no intentionthat in the use of such terms and expressions of excluding anyequivalents of the features shown and described or portions thereof, butit is recognized that various modifications are possible within thescope of the invention claimed. Thus, it should be understood thatalthough the present invention has been specifically disclosed herein,optional features, modification and variation of the concepts hereindisclosed may be resorted to by those skilled in the art, and that suchmodifications and variations are considered to be within the scope ofthis invention as defined by the appended claims. In addition, wherefeatures or aspects of the invention are described in terms of Markushgroups, those skilled in the art will recognize that the invention isalso thereby described in terms of any individual member or subgroup ofmembers of the Markush group.

The invention has been described broadly and generically herein. Each ofthe narrower species and subgeneric groupings falling within the genericdisclosure also form part of the invention. This includes the genericdescription of the invention with a proviso or negative limitationremoving any subject matter from the genus, regardless of whether or notthe excised material is specifically recited herein. Other aspects ofthe invention are within the following claims.

All publications, patents and patent applications mentioned in thisspecification are indicative of the level of skill of those skilled inthe art to which this invention pertains, and are herein incorporated byreference to the same extent as if each individual publication, patentor patent application was specifically and individually indicated to beincorporated by reference.

1. A method of reducing/recycling polystyrene foam comprising the stepsof (a) providing polystyrene foam; (b) applying to said polystyrene foama solution comprising: one or more standard dibasic ester (DBE)compositions selected from the group consisting of dimethyl glutarate,dimethyl adipate, and dimethyl succinate; (c) subjecting the resultantpolygel to a low source of heat over a temperature range not to exceed200-300° C.; (d) subjecting the resultant polygel to one or moreextruders over a temperature range not to exceed 200-300° C.; and (e)recapturing the dibasic esters; wherein said recaptured dibasic estersare reused or recycled and the resultant polystyrene foam polygel may berecycled into high quality beaded polystyrene foam.
 2. A method ofreducing/recycling polystyrene foam comprising the steps of (a)providing polystyrene foam; (b) applying to said polystyrene foam asolution comprising: one or more low vapor pressure dibasic ester(LVP-DBE) compositions selected from the group consisting of dimethylglutarate, dimethyl adipate, and dimethyl succinate; (c) subjecting theresultant polygel to a low source of heat over a temperature range notto exceed 200-300° C.; (d) subjecting the resultant polygel to one ormore extruders over a temperature range not to exceed 200-300° C.; and(e) recapturing the low vapor pressure dibasic esters; and wherein saidrecaptured low vapor pressure dibasic esters are reused or recycled andthe resultant polystyrene foam polygel may be recycled into high qualitybeaded polystyrene foam.
 3. A method of reducing/recycling polystyrenefoam comprising the steps of (a) providing polystyrene foam; (b)applying to said polystyrene foam a solution comprising: (i) one or moreterpenes or isopernoids or any combination thereof and (ii) one or moresurfactants; (c) subjecting the resultant polygel to a low source ofheat over a temperature range not to exceed 200-300° C.; (d) subjectingthe resultant polygel to one or more extruders over a temperature rangenot to exceed 200-300° C.; and (e) recapturing the terpenes orisopernoids; and wherein said recaptured terpenes or isopernoids arereused or recycled and the resultant polystyrene foam polygel may berecycled into high quality beaded polystyrene foam.
 4. A polystyrene lowheat treatment extruder recycling system comprising the steps of (a)exposing polystyrene foam in a container to a solution of specificesters comprising dimethyl glutrate [CAS # 1119-40-0] and dimethyladipate [CAS# 627-93-0], wherein the esters specifically excludedimethyl succinate in weight percentage amounts greater than 1%; (b)optionally covering said container; (c) subjecting the resultant polygelto a low source of heat over a temperature range not to exceed 200-300°C.; (d) subjecting the resultant polygel to one or more extruders over atemperature range not to exceed 200-300° C.; (e) optionallysupplementing polystyrene foam until maximum reduction is achieved and(f) recapturing the dibasic esters; and wherein said recaptured dibasicesters are reused or recycled and the resultant polystyrene foam polygelmay be recycled into high quality beaded polystyrene foam.
 5. A methodof reducing/recycling polystyrene foam comprising the steps of (a)providing polystyrene foam; (b) applying to said polystyrene foam asolution comprising: (i) one or more low vapor pressure dibasic estercompositions selected from the group consisting of dimethyl glutarate,dimethyl adipate, and dimethyl succinate; (ii) one or more dibasic estercompositions selected from the group consisting of dimethyl glutarate,dimethyl adipate, and dimethyl succinate or (iii) (a) one or moreterpenes or isopernoids or any combination thereof and (b) one or moresurfactants; or any combination thereof of (i)-(iii); (c) subjecting thepolygel to a low source of heat over a temperature range not to exceed200-300° C.; (d) subjecting the polygel to one or more extruders over atemperature range not to exceed 200-300° C.; and (e) recapturing thedibasic esters, the low vapor pressure dibasic esters and/or theterpenes or isopernoids; and wherein said recaptured dibasic esters, lowvapor pressure dibasic esters and/or the terpenes or isopernoids arereused or recycled and the resultant polystyrene foam polygel may berecycled into high quality beaded polystyrene foam.
 6. A polystyrene lowheat treatment extruder recycling system comprising an LVP-DBEcomposition that exhibits one or more of the following characteristics:(a) a significantly lower vapor pressure than standard DBE, (b) thedistillation range of the solvent is narrower, (c) chemically morestable than standard DBE, (d) that is incompatible or can react with,inter alia, strong oxidizers, acids, alkalies, etc., (e) that will notundergo polymerization, (f) that reduces foamed polystyrene at a rate ofaction that equals or exceeds that of standard DBE, (g) that exhibits agreater holding capacity than standard DBE, (h) that exhibits a higherflash point than standard DBE, (i) that is not regulated as a hazardousmaterial by DOT, IMO, or IATA, and (j) for which none of the componentspresent in the LVP-DBE composition are listed by IARC, NTP, OSHA orACGIH as a carcinogen.
 7. A polystyrene low heat treatment extruderrecycling system comprising exposing said foams to liquid sprays ofspecific esters exhibiting one or more of the aforementionedcharacteristics.
 8. A polystyrene low heat treatment extruder recyclingsystem comprising exposing said foams to liquid sprays of specificesters comprising dimethyl glutarate [CAS # 1119-40-0] and dimethyladipate [CAS# 627-93-0], wherein the ester specifically excludesdimethyl succinate in weight percentage amounts greater than 1%, andwherein said esters exhibit one or more of the aforementionedcharacteristics.
 9. A polystyrene low heat treatment extruder recyclingsystem comprising exposing said foams to liquid sprays of specificesters, wherein the ester is selected from the group consisting ofdimethyl glutarate [CAS # 1119-40-0] and dimethyl adipate [CAS#627-93-0], wherein the esters specifically exclude dimethyl succinate inweight percentage amounts greater than 1%, and wherein said estersexhibit one or more of the aforementioned characteristics.
 10. Themethod of claims 1-9, wherein step (b) of adding the solution comprisingthe dibasic esters, the low vapor pressure dibasic esters, and/or theterpenes or isopernoids or any combination thereof is carried outwithout prior treatment of the polystyrene foam with one or more thinfilm evaporators or one or more fluffers, and/or one or more dryers. 11.The method of claims 1-9, wherein after the step of recapturing thedibasic esters, the low vapor pressure dibasic esters and/or theterpenes or isopernoids, the resultant polystyrene polygel is optionallybe subjected to one or more thin film evaporators (TFEs) for a timeperiod of approximately 1-2 minutes, but not to exceed approximately 10minutes.
 12. The method of claims 1-9, wherein the resultant highquality beaded polystyrene product exhibits a series of propertiescomprising a heat index of less than about 9, concentration of less thanabout 1-1000 ppm, and/or no evidence of spleaning, crazing or burntdiscoloration, low melt viscosity or molecular weight, or anycombination thereof.
 13. The method of claims 1-9, wherein thepolystyrene foam products are subject to the vapor of low vapor pressuredibasic esters in an enclosed area for a period of time until they arereduced to a gelatenous state or close to a viscous state.
 14. Themethod of claim 13, wherein said polystyrene foams are reduced in volumeby the effect of sprayed liquids containing low vapor pressure dibasicesters in addition to said vapors.
 15. The method of claim 13, whereinsaid enclosed area is a plastic bag, drum, or any other closedcontainer.
 16. A recycling system to reduce the volume of polystyrenefoams wherein said polystyrene foams are exposed to vapors of low vaporpressure dibasic esters over an extended period in a container whichprevents escape of said vapors, liquid or a combination thereof.
 17. Therecycling system of claim 16, wherein said vapors are contained in atank or vessel which has ports for addition of polystyrene foams, foraddition of low vapor pressure dibasic esters, and for withdrawal ofdissolved polystyrene or polygel.
 18. The recycling system of claim 17,wherein said vapors arise from a combination of a spray of the liquidlow vapor pressure dibasic esters and vapors transported from a secondtank, and the polystyrene foam in its reduced state is withdrawn by flowto said second tank.